Schizophrenia is associated with prominent declarative memory performance (DMP) deficits for which there is no specific treatment. DMP is a medial temporal lobe (MTL) function and there is strong evidence for an early MTL injury in schizophrenia making this a model disease for studying for studying the interactive effects of aging and disease on MTL function. The investigators have tested the cognitive effects of controlled hyperglycemia/hyperinsulinemia as a putative regulator of energy transport within the MTL, finding selective DMP improvement in normal younger and older adults and in patients with schizophrenia an Alzheimer's type dementia, noting preliminary evidence for age-and disease-related shifts to the right in the dose-response relationship of plasma glucose and/or insulin levels to memory performance.